You can say that some cloud mining is a ponzi, but I think it is wrong to say that all of them are.  I have good experience with hashnest.  But you have to understand the risks involved, like the difficulty increase and that they are making a new generation of asics soon.  But the nice thing is that you can still sell at any time the hash you bought without a transaction fee.  Looking at the market even s2 hash is still for sale, so I think that it is ok to get some s5 with the next generation coming.

Sure there are ponzis like BCS, but that is why you must research before you buy into any cloud service.  But you can;t say with a straight face that they are all ponzis.  Just because you did not make money does not mean that the investment is bad.